1. Field of the Invention
The present invention relates to audible tone generator means and more particularly to circuit means for providing various electrical signals whereby the audible tone generator means produces a plurality of distinguishable audible signals in response to the various electrical signals.
Generally speaking, the circuit means of the present invention includes at least two gates wherein the output of one of the gates determines the type of audible signal produced by the audible tone generator means. The circuit includes a single control terminal for controlling the logical state of the output of the one gate and for therefore controlling the type of audible signal produced by the audible tone generator means.
2. Description of the Prior Art
A number of audible tone generator devices are well known to those skilled in the art such as a piezoelectric transducer, an electromechanical buzzer, a horn, a speaker, etc. With the appropriate drive circuit means electrically coupled to these conventional audible tone generator devices they can be driven to produce a single audible signal.
Many times it is desirable that a single audible tone generator device produce two or more distinguishable audible signals to indicate the existence or nonexistence of two or more conditions. Accordingly, either an additional drive circuit is required or the original drive circuit must be changed in some fashion to provide a different electrical drive signal for each condition.
In U.S. Pat. No. 3,922,672 issued Nov. 25, 1975 to Thomas W. Birt, et al. a drive circuit means is disclosed which is capable of providing different electrical signals whereby an audible tone generator means produces two distinguishable audible signals. As disclosed in the Birt, et al. patent, the drive circuit means requires at least two control terminals to provide the different electrical signals which will produce the two audible signals. Accordingly, one input of each of the logic gates included in the Birt, et al. drive circuit means are controlled by an external electrical signal applied at each of the control terminals electrically coupled thereto.
The present invention accomplishes the same result as the Birt, et al. drive circuit means described hereinabove utilizing fewer electrical components by requiring only one control terminal for controlling an input of only one of the logic gates.